A medicament delivery device may comprise a number of components that are manufactured and assembled in order to provide the desired functions. The medicament delivery devices often comprise elongated housing parts that are arranged to house the assembled components. These may for example include power units or drive mechanisms that are capable of delivering forces when activated, which forces may be used for performing different functions such as e.g. penetration and injection if the medicament delivery device is an injection device.
In many cases the drive mechanisms are assembled with the power source, often a compression drive spring, in a tensioned state. The drive springs are often held in this tensioned state by components of the unit and do not in that non-active state exert any force on the housing of the medicament delivery device.
When the components are assembled inside the housing, it is often enclosed by some sort of enclosure cap, such as an end cap that is attached. The attachment may be performed in many ways such as gluing, plastic welding, screw threads or bayonet threads. These attachment means often provide a secure attachment, but are not optimal from an assembly point of view since they either take quite an amount of time to perform an attachment, or they make the moulding dies complicated in order to get the form and the required tolerances, which increases the manufacturing costs. This may not be acceptable if for example the medicament delivery device is a so called disposable that is thrown or discarded after us.
Therefore, flexible arms with snap-in attachments are often used, providing a fast assembly operation, with moderately complicated forms. However, since the flexibility is utilized when assembly is performed, there is a risk that the attachment is disengaged during use. This risk is especially pronounced if the attachment is exposed to a force, which may be the case when the medicament delivery device is activated and for example a drive spring is released. In order for the spring to exert a force on a medicament container for expelling a dose of medicament, the other end of the spring has to have a fixed support, which in many cases may constitute a surface of the end cap.
This may be a major drawback because the medicament delivery device may then break leading on the one hand to a non-delivery of medicament and on the other hand may injure the user.